7. Air filter

Most often out of sight and out of mind, the air filter deserves better, and a place on your car part replacement calendar is a start. Try running with your hand over your mouth, and you’ll get an idea how much your engine depends on air. That air for the engine and airflow sensor still has to be free of contaminates, though, and that’s your air filter’s job. Be aware of manufacturer recommendations for replacing related airflow components like the PCV valve and oxygen sensor, if your car has them.